United B38M at Newark on Feb 6th 2024, stuck rudder pedals on landing
Last Update: March 7, 2024 / 20:44:03 GMT/Zulu time
Incident Facts
Date of incident
Feb 6, 2024
Classification
Incident
Airline
United
Flight number
UA-1539
Departure
Nassau, Bahamas
Destination
Newark, United States
Aircraft Registration
N47280
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
The aircraft underwent a test flight the following day during which the anomaly was replicated.
On Mar 7th 2024 the NTSB reported:
In a post-incident statement, the captain reported that during the landing rollout, the rudder pedals did not move in response to the “normal” application of foot pressure while attempting to maintain the runway centerline. The pedals remained “stuck” in their neutral position. The captain used the nosewheel steering tiller to keep the airplane near the runway centerline while slowing to a safe taxi speed before exiting the runway onto a high-speed turn-off. While on the high-speed turnoff, the captain asked the first officer to check his rudder pedals and he reported the same problem. The captain reported, that shortly thereafter, the rudder pedals began to operate normally. After parking the aircraft, the flight crew notified UAL maintenance of the flight control malfunction. The airplane was removed from service for maintenance and troubleshooting.
A review of preliminary flight data recorder (FDR) data corroborated the pilot’s statements regarding the malfunction of the rudder system. Data showed that during the landing and subsequent rollout, the rudder surface position remained near its neutral position even though the force inputs to the rudder pedals were observed to be increasing. About 30 seconds after touchdown, a significant pedal force input was observed along with corresponding rudder surface movement. Afterward, the rudder pedals and rudder surface began moving as commanded and continued to function normally for the remainder of the taxi.
On February 9, 2024, UAL conducted a test flight on the event airplane at EWR and was able to duplicate the reported rudder system malfunction identified during the incident. As a result, the test flight profile was discontinued, and the airplane returned to EWR and landed uneventfully.
The NTSB was notified of the flight control issue after the flight test and an incident investigation was started.
The NTSB further reported:
Post-incident troubleshooting and inspection of the rudder control system found no obvious malfunctions with the system or any of its components whose failure would have resulted in the restricted movement observed during flight 1539 and the test flight. As a precaution, the aft rudder input torque tube and associated upper and lower bearings and the rudder rollout guidance servo were removed for further examination by the NTSB systems group.
...
On February 28, 2024, the Systems group met at the Collins Aerospace facility in Cedar Rapids, Iowa to examine and test the SVO-730 rollout guidance servo removed from the incident airplane. The testing was conducted to evaluate the effects that temperature “cold soaking” of the servo might have on the torque required to move the servo’s output crank arm. Testing at room temperature found that the torque to rotate the servo’s output crank arm was within design specifications. The unit was then “cold soaked” for 1 hour and the test was repeated. That testing found that the torque to move the servo’s output crank arm was significantly beyond the specified design limits. Because the servo output crank arm is mechanically connected to the rudder input torque tube, the restricted movement of the servo’s output crank arm would prevent the rudder pedals from moving as observed during flight 1539 and the test flight. Further examination of the SVO-730 rollout guidance servo will be conducted as the investigation continues.
Aircraft Registration Data
Incident Facts
Date of incident
Feb 6, 2024
Classification
Incident
Airline
United
Flight number
UA-1539
Departure
Nassau, Bahamas
Destination
Newark, United States
Aircraft Registration
N47280
Aircraft Type
Boeing 737-800MAX
ICAO Type Designator
B38M
This article is published under license from Avherald.com. © of text by Avherald.com.
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